Thin layer deposition process

ABSTRACT

A method of preventing out-gassing from lift-off structures formed of positive resists (as for example, o-quinone diazide/phenol formaldehyde novolak resins) during vacuum evaporation of metals in the fabrication of semiconductor devices. Such outgassing is avoided by compositional control of the photosensitive resist lift-off layer and by providing an additional baking step after the lift-off mask has been formed. Both conditions are required and critical to avoid the volatile resin decomposition products which not only tend to contaminate the device substrate surface, but also the deposited metal film. The method employs a photosensitive polymer which contains about 10 to 20 wt. % of the sensitizer (e.g. o-quinone diazide) in conjunction with a secondary baking step at about 160° to about 200° C. after the lift-off mask has been formed and prior to metal film deposition. As a result the method provides an improved metal film as well as increased through-put, particularly when forming Schottky barrier diode contacts.



